RT-N66R shows unmounted

[dayscomputerservices]

And stupid Western Digital doesn't read their notes of my troubleshooting I've done. Its really getting old that I know more than the people I call for L2 or L3 questions

 

[dayscomputerservices]

MERGED QUESTION
Question from dayscomputerservices : "RT-AC66r shows unmounted"

If everything is working on other computers, what is the most common reason for this "unmounted" messaged?